Method and apparatus for increasing blood flow through an obstructed blood vessel

ABSTRACT

A method of increasing blood flow through an obstructed blood vessel includes providing an expandable member substantially made of a mesh having a plurality of interstices. The expandable member is inserted into the blood vessel, positioned within the blood vessel with the proximal member end upstream of the distal member end and the member body located radially adjacent at least a portion of an obstruction, and expanded to bring at least a portion of the member body into contact with the obstruction. An outward radial force is exerted on the obstruction to dislodge at least one fragment from the obstruction and to enhance blood flow through the blood vessel past the obstruction. The at least one fragment is passed through at least one interstice of the member body in the radial direction, and is selectively retained within the expandable member.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 13/184,359,filed Jul. 15, 2011, which is a divisional of application Ser. No.11/700,987, filed Feb. 1, 2007, which is incorporated by reference inits entirety herein, and which claims priority from U.S. ProvisionalApplication No. 60/764,206, filed Feb. 1, 2006 and U.S. ProvisionalApplication No. 60/793,588, filed Apr. 20, 2006, the subject matter ofboth of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an apparatus and method for increasingblood flow through an obstructed blood vessel and, more particularly, toa method and apparatus for using an expandable member to increase bloodflow through an obstructed blood vessel.

BACKGROUND OF THE INVENTION

Vascular disease involves damage that happens to the blood vessels inthe body. Diseased blood vessels can become plugged with thrombus,plaque, clots, grumous material, and/or other unwanted matter (hereafter“obstructions”) that may ultimately lead to a condition known asischemia. Ischemia refers to a substantial reduction or loss of bloodflow to the brain or any other tissue that is being supplied by theblood vessel and can lead to permanent damage of the affected region.While vascular disease is most commonly associated with the formation ofhard plaque and coronary artery disease in the heart, similar damage canhappen to many other vessels in the body, such as the peripheral vesselsand cerebral vessels, due to the buildup of obstructions, including hardplaque or softer thrombus/grumous material, within the lumen of anartery or vein.

A variety of vascular medical devices and procedures have been developedto treat diseased vessels. The current standard procedures includebypass surgery (where a new blood vessel is grafted around a narrowed orblocked artery) and several different types of non-surgicalinterventional vascular medical procedures, including angioplasty (aballoon on a catheter is inflated inside a narrowed or blocked portionof an artery in an attempt to push back the obstruction), lytic therapy(pharmaceutical agents are employed to chemically fragment theobstruction), stenting (a metal mesh tube is expanded against a narrowedor blocked portion of an artery to hold back the obstruction), anddebulking techniques in the form of atherectomy (a high speed or highpower mechanism is used to dislodge or mechanically abrade a hardenedobstruction) or thrombectomy (a mechanism or infused fluid is used todislodge/remove the obstruction). In each of these interventionalvascular medical procedures, a thin, flexible guidewire is routedthrough the patient's vascular system to a desired treatment locationand then a catheter, carrying a device appropriate for the givenprocedure, is tracked along the guidewire to the treatment location.

Although interventional vascular procedures avoid many of thecomplications involved in surgery, there is a possibility ofcomplications if some of the obstruction breaks free and flowsdownstream in the blood vessel or into a connected blood vessel,potentially causing a stroke, a myocardial infarction (heart attack), orother tissue death. One solution to this potential complication is touse some kind of occlusive device or filtering device to block or screenthe blood flowing downstream of the treatment location.

An example of a vascular filter is disclosed in U.S. Patent ApplicationPublication No. 2002/0111648, published Aug. 15, 2002 by Richard S.Kusleika et al. (hereafter referenced as “the '648 publication”). The'648 publication discloses a collapsible medical device including aradially expandable body having proximal and distal sliders slidablyattached to a mandrel (Abstract). The medical device is placed at apredetermined treatment site, such as a convenient location in apatient's vasculature positioned distally of an obstruction which willbe treated with an angioplasty balloon or an atherectomy device(paragraph 0066). At least one embodiment of the medical device of the'648 publication can be used to filter fluid which is passing through avessel and also can either temporarily or permanently occlude thevessel. The medical device of the '648 publication, however, may causeundue mechanical trauma or irritation to a previously healthy portion ofthe blood vessel because of the remote deployment from the obstructionsite. Moreover, temporary or permanent occlusion of the blood vessel maycause ischemia and/or additional clotting of stagnant blood, thus addingto any such damage already caused by the unwanted obstruction.

SUMMARY OF THE INVENTION

In an embodiment of the present invention, a method of increasing bloodflow through an obstructed blood vessel is described. An expandablemember substantially made of a mesh having a plurality of interstices isprovided. The expandable member has a proximal member end and a distalmember end spaced longitudinally apart by a tubular member body. Theexpandable member is substantially closed at the distal member end. Theexpandable member is inserted into the blood vessel. The expandablemember is positioned within the blood vessel with the proximal memberend upstream of the distal member end and the member body locatedradially adjacent at least a portion of an obstruction. The expandablemember is expanded to bring at least a portion of the member body intocontact with the obstruction. An outward radial force is exerted on theobstruction to dislodge at least one fragment from the obstruction andto enhance blood flow through the blood vessel past the obstruction. Theat least one fragment is passed through at least one interstice of themember body in the radial direction. The at least one fragment isselectively retained within the expandable member.

In an embodiment of the present invention, an expandable member isdescribed. The expandable member includes a proximal member end and adistal member end, longitudinally spaced from the proximal member end. Atubular member body extends between the proximal and distal member endsand is adapted to selectively contact at least a portion of anobstruction within a blood vessel in a radial direction, to dislodge atleast one fragment from the obstruction, and to enhance blood flowthrough the blood vessel past the obstruction. At least one of theproximal and distal member ends is closed. The member body is made of afirst mesh having a plurality of first interstices. At least one of thefirst interstices is adapted to allow passage of at least one fragmenttherethrough in a radial direction into the member body. A closed one ofthe proximal and distal member ends is made of a second mesh having aplurality of second interstices. At least one of the second intersticesis adapted to selectively allow passage of at least one fragmenttherethrough.

In an embodiment of the present invention, an apparatus for increasingblood flow through an obstructed blood vessel is described. A deliverycatheter has proximal and distal catheter ends separated by a hollowcatheter lumen and defining a longitudinal axis. The distal catheter endis adapted for placement within the blood vessel adjacent anobstruction. A guidewire has proximal and distal guidewire endslongitudinally separated by a guidewire body. The guidewire is adaptedfor selective insertion through the catheter lumen. An expandable memberis removably attached to the guidewire adjacent the distal guidewireend; is selectively moveable between a first, collapsed condition and asecond, expanded condition; and is adapted for passage through thecatheter lumen in the collapsed condition and selective release from thecatheter lumen and placement into the expanded condition adjacent theobstruction. The expandable member includes a proximal member end and adistal member end, longitudinally spaced from the proximal member end. Atubular member body extends between the proximal and distal member endsand is adapted to selectively contact at least a portion of theobstruction in a radial direction, to dislodge at least one fragmentfrom the obstruction and to enhance blood flow through the blood vesselpast the obstruction, when the expandable member is in the expandedcondition. At least one of the proximal and distal member ends isclosed. The tubular member body is made of a first mesh having aplurality of first interstices. At least one of the first interstices isadapted to allow passage of the at least one fragment therethrough in aradial direction into the member body. A closed one of the proximal anddistal member ends is made of a second mesh having a plurality of secondinterstices. At least one of the second interstices is adapted toselectively allow passage of the at least one fragment therethrough.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be made tothe accompanying drawings, in which:

FIG. 1 is a side view of a first embodiment of the present invention;

FIG. 2 is a side view of a second embodiment of the present invention;

FIG. 3 is a side view of a third embodiment of the present invention;

FIG. 4 is a side view of a fourth embodiment of the present invention;

FIG. 5 is a side view of a fifth embodiment of the present invention;

FIGS. 6A-6C are partial sectional views depicting the embodiment of FIG.1 in a first mode of operation;

FIGS. 7A-7D are partial sectional views depicting the embodiment of FIG.1 in a second mode of operation; and

FIGS. 8A-8E are partial sectional views depicting a mechanism ofoperation of any embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, FIG. 1 depicts a firstarrangement of an expandable member 100 for increasing blood flowthrough an obstructed blood vessel. The expandable member 100 defines alongitudinal axis 102, which may be rectilinear or curvilinear. Theexpandable member 100 has a proximal member end 104 longitudinallyspaced from a distal member end 106. The terms “proximal” and “distal”refer to orientations inside a patient's body with respect to a user,with a proximal location being nearer to an insertion point into thebody than a distal location. It should be realized, however, thatstructures and deployment may be oriented differently for a particularapplication and that the terms “proximal” and “distal” are used hereinfor ease of description without limiting the present invention. At leastone of the proximal and distal member ends 104 and 106 is closed, with aclosed end, depicted as the proximal member end in FIG. 1, beingpositioned further downstream in a blood vessel than the rest of theexpandable member 100. The expandable member 100 is selectively moveablebetween a first, collapsed condition and a second, expanded condition.

A tubular member body 108 extends between the proximal and distal memberends 104 and 106. The member body 108 is adapted to selectively contactat least a portion of an obstruction within a blood vessel in a radialdirection, the radial direction being defined with respect to thelongitudinal axis 102, and may exert a compressive force upon theobstruction. The member body 108 is also adapted to dislodge at leastone fragment from the obstruction and to enhance blood flow through theblood vessel past the obstruction, with these functions being describedin further detail below.

The member body 108 is made of a first mesh 110 having a plurality offirst interstices 112. Each of the first interstices 112 is defined by aplurality of first strands 114. At least one of the first interstices112 is adapted to allow passage of at least one fragment therethrough ina radial direction into the member body 108. A closed one of theproximal and distal member ends 104 and 106 (as shown in FIG. 1, theproximal member end) is made of a second mesh 116 having a plurality ofsecond interstices 118. Each of the second interstices 118 is defined bya plurality of second strands 120. At least one of the secondinterstices 118 is adapted to selectively allow passage of at least onefragment therethrough. Many of the first and second interstices 112 and118 and first and second strands 114 and 120 are left unlabeled in theFigures for clarity of depiction. Though the first interstices 112 aredepicted in certain of the Figures as being larger than the secondinterstices 118 when there is an optional size difference between thetwo, the second interstices could instead be larger than the firstinterstices. Similarly, the sizes of the first interstices 112 couldvary from one another and the sizes of the second interstices 118 neednot be uniform either. It is contemplated that there could even be anoverlap in size ranges between the first and second interstices 112 and118.

Each of the first and second strands 114 and 120 may be oriented in atleast one of a helical, longitudinal, and radial direction with respectto the member body 108. The first and second strands 114 and 120 mayeach be formed of any desired material or combination of materials,including, but not limited to, a metal, an alloy, a composite, apolymer, and the like. For example, the first and second strands 114 and120 may each be made of nitinol, stainless steel, cobalt chromium,platinum, titanium, plastic, or any combination thereof. The first andsecond strands 114 and 120 may each have a diameter between about 10-250microns, e.g., about 50 microns. Any of the first and second strands 114and 120 may have a cross-sectional shape along at least a portionthereof which is designed to augment the performance of the expandablemember 100 as described below. For example, the cross-sectional shapemay include an angle designed to concentrate outward force of theexpandable member at a specific portion of the strand cross-sectionperiphery. Likewise, at least a portion of any of the first and secondstrands 114 and 120 could be coated with a material designed to producea desired mechanical effect (e.g., cushioning, erosion, or any othereffect) upon a surface contacted by the coated portion of the strand.

The first and second meshes 110 and 116 may be formed integrally or maybe separately formed and attached together during manufacture of theexpandable member 100. The first and second meshes 110 and 114 may eachbe at least partially constructed of a shape-memory material, such asnitinol. The first and second meshes 110 and 114 may be formed in anydesired manner, including, but not limited to, braiding, welding,molding, weaving, laser-cutting a tube or sheet, and the like. The firstand second meshes 110 and 114 should be configured for desireddeployment characteristics, as described below, and to providesufficient flexibility for tracking through a possibly tortuous vascularsystem of an individual, such as the intracranial vascular system.

Though the closed distal member end 106 is depicted in the Figures ashaving a tapered shape, the closed one (or both) of the proximal anddistal member ends 104 and 106 can be of any suitable shape, such as,but not limited to, tubular, conical, convex, concave, or any othershape. Both of the proximal and distal member ends 104 and 106, whenclosed, may be made from the first mesh 110, the second mesh 116, or anyother mesh (not shown) and need not be made from the same mesh. Thebelow description will presume that each closed end is made from thesecond mesh 116. The shape of the closed one of the proximal and distalmember ends 104 and 106 may be coincidentally produced by the methodused to form the closed end(s) or may be formed intentionally for adesired performance effect.

The member body 108 defines a body interior 122. The expandable member100 may include a guidewire 124 extending longitudinally between theproximal and distal member ends 104 and 106 through the body interior122. The guidewire 124 may have an operative length 126 between theproximal and distal member ends 104 and 106 of between about 0.5-50 mm,e.g., about 22 mm. When present, the guidewire 124 has a proximalguidewire end (not shown) longitudinally separated from a distalguidewire end 128 by a guidewire body 130. The operative length 126 ofthe guidewire 124, between the proximal and distal member ends 104 and106, is located adjacent the distal guidewire end 128.

The guidewire 124 may help push or pull the expandable member 100through the vascular system to a desired deployment location. To thisend, any suitable portion of the expandable member 100 may be attachedto the guidewire 124 in a permanent manner (e.g., welding, crimping,soldering, adhesives, or the like) or by a temporary, releasableconnection. If the latter, the connection mechanism (not shown) shouldbe designed to be selectively releasable by the user as discussed below.The guidewire body 130 has a length sufficient to extend through thevascular system to place the expandable member 100 in the desireddeployment location. For example, when the guidewire 124 islongitudinally connected to another structure (not shown) for moving theexpandable member 100, the guidewire body 130 will be shorter than ifthe guidewire is the only structure that moves the expandable member.The guidewire body 130 may have a length of between about 0.5 mm-200 cm,e.g., about 150 cm. The diameter of the guidewire body 130 may varyalong the length of the guidewire body or may be constant. For example,the diameter of the guidewire body 130 toward the proximal guidewire endmay be between about 0.2-1 mm, e.g., about 0.36 mm, while the diameterof the operative length 126 portion of the guidewire body may be betweenabout 0.05-1 mm, e.g., about 0.15 mm.

For clarity of description, the proximal member end 104 will bedescribed below as being attached to the guidewire at or adjacent thedistal guidewire end 128, unless otherwise specifically indicated.Regardless of the attachment type or means, the guidewire 124 may extendbeyond at least one of the proximal and distal member ends 104 and 106to support the expandable member 100, and may be adapted to removably orpermanently attach the expandable member to a delivery system (notshown). The guidewire 124, when affixed, can facilitate minor changes inthe position of the expandable member 100 during use and also canincrease positional stability of the expandable member.

The expandable member 100 may include at least one radiopaque portion,such as the attachment collar 132 shown in FIG. 1, to facilitate remotevisualization using, for example, one or more of fluoroscopy, computertomography (CT) fluoroscopy, magnetic resonance, or the like. Theradiopaque portion could be a structure of the expandable member 100made of a radiopaque material or could be a separate radiopaquemarker/material attached to or coated on at least a portion of theexpandable member. For example, a thin layer of platinum could besprayed, electroplated, or otherwise coated onto at least a portion ofthe expandable member 100.

Optionally, the expandable member 100 may be at least partially adaptedto elute a pharmaceutical agent (not shown). As used herein, “eluting”means releasing, leaching, diffusing, or otherwise providing apharmaceutical agent to a target area. The pharmaceutical agent may beimpregnated in or coated on at least a portion of the expandable member100, provided through a fluid connection between the expandable memberand a pharmaceutical source (not shown), or otherwise directed to thetarget area via the expandable member 100. Alternately or additionally,a pharmaceutical agent may be provided to the patient locally orsystemically in any desired dosage, using a mechanism other than theexpandable member 100. Examples of suitable pharmaceutical agents forprovision in any suitable manner include thrombolytic medication,anti-platelet medication, anti-thrombotic medication, a plasminogenactivator (e.g., tPA, urokinase, streptokinase, desmotoplase), aIIb/IIIa inhibitor (e.g., abiciximab, tirofiban, eptifatide), a thrombininhibitor (e.g., heparin, bivalirudin), or any combinations thereof.

FIG. 2 depicts a second embodiment of an expandable member 100 baccording to the present invention. The expandable member 100 b of FIG.2 is similar to the expandable member 100 of FIG. 1 and therefore,structures of FIG. 2 that are the same as or similar to those describedwith reference to FIG. 1 have the same reference numbers with theaddition of a “b”. Description of common elements and operation similarto those in the previously described embodiment will not be repeatedwith respect to the second embodiment.

As with the first embodiment, the first and second meshes 110 b and 116b of the second embodiment may be formed integrally or may be separatelyprovided and attached before use. As shown in FIG. 2, however, at leastone of the plurality of second interstices 118 b may be smaller than atleast one of the plurality of first interstices 112 b.

FIG. 3 depicts a third embodiment of an expandable member 100 caccording to the present invention. The expandable member 100 c of FIG.3 is similar to the expandable member 100 of FIG. 1 and therefore,structures of FIG. 3 that are the same as or similar to those describedwith reference to FIG. 1 have the same reference numbers with theaddition of a “c”. Description of common elements and operation similarto those in the previously described embodiments will not be repeatedwith respect to the third embodiment.

In the third embodiment, and as shown in FIG. 3, both the proximal anddistal ends 104 c and 106 c are closed. Additionally, the proximal anddistal ends 104 c and 106 c are both shown as being connected to theguidewire 124 c through attachment collars 132 c. Either or both of theattachment collars 132 c depicted in FIG. 3, or any other portions ofthe expandable member 100 c, may be radiopaque.

FIG. 4 depicts a fourth embodiment of an expandable member 100 daccording to the present invention. The expandable member 100 d of FIG.4 is similar to the expandable member 100 of FIG. 1 and therefore,structures of FIG. 4 that are the same as or similar to those describedwith reference to FIG. 1 have the same reference numbers with theaddition of a “d”. Description of common elements and operation similarto those in the previously described embodiments will not be repeatedwith respect to the fourth embodiment.

Similarly to the second embodiment, the fourth embodiment includes firstinterstices 112 d which are a different size than the second interstices118 d. The expandable member 100 d shown in FIG. 4 omits the previouslydescribed guidewire. However, one of ordinary skill in the art canreadily design a suitable deployment mechanism for an expandable member100 d lacking a guidewire, and the description of operation of thepresent invention (below) will presume that a guidewire is present,notwithstanding the depiction of FIG. 4.

FIG. 5 depicts a fifth embodiment of an expandable member 100 eaccording to the present invention. The expandable member 100 e of FIG.5 is similar to the expandable member 100 of FIG. 1 and therefore,structures of FIG. 5 that are the same as or similar to those describedwith reference to FIG. 1 have the same reference numbers with theaddition of a “e”. Description of common elements and operation similarto those in the previously described embodiment will not be repeatedwith respect to the fifth embodiment.

FIG. 5 illustrates an expandable member 100 e similar to that of thethird embodiment, in which both the proximal and distal ends 104 e and106 e are closed. Additionally, the proximal and distal ends 104 e and106 e are both shown as being connected to the guidewire 124 e throughattachment collars 132 e. The proximal end 104 e is not made of atightly woven mesh, however, but instead includes a small number ofsecond strands 120 e (four shown) linking the member body 108 e to theattachment collar 132 e.

Regardless of the embodiment of the expandable member 100, the presentinvention may be used to help increase blood flow through an obstructedblood vessel by both compressing and fragmenting the obstructing matter.FIGS. 6A-6C and 7A-7D depict first and second modes of operation,respectively, of the deployment of an expandable member 100 according tothe present invention. Although the expandable member 100 is describedin a vascular application, the present invention may readily be used inother body lumens, as will be appreciated by one of ordinary skill inthe art.

A delivery catheter 232 may be inserted into a blood vessel 234 in anysuitable manner, such as through the use of endovascular, percutaneous,or other minimally invasive surgical techniques. The delivery catheter232 defines a longitudinal axis 236, which may be rectilinear orcurvilinear. The delivery catheter 232 has proximal and distal catheterends 238 and 240, respectively, separated by a hollow catheter lumen242. The distal catheter end 240 is adapted for placement within theblood vessel 234 adjacent an obstruction 244, as shown in FIG. 6A. Anonlimiting example of a suitable delivery catheter is one of theExcelsior line of microcatheters, available from Boston Scientific ofNatick, Mass. The 1.5-3 French sized Excelsior microcatheters, forexample, may be useful in an intracranial application of the presentinvention.

The obstruction 244 may include any material that fully or partiallyblocks a blood vessel 234, such as a thrombus. The thrombus can arisedue to conditions such as a cardioembolism, a carotid bifurcation, or aniatrogenic cause of idiopathic or cryptogenic etiology. Plaque, clots,grumous material, and/or other unwanted matter could also or insteadform the obstruction 244. Several of the Figures are partial side orsectional views depicting the obstruction 244 in cross-section as acylindrical obstruction lining the blood vessel 234, but discontinuouspatches of obstruction could also or instead be present. The obstruction244 may not be tightly adhered to the blood vessel 234, but may beloosely held in position within the blood vessel, or could even befloating freely in the body. In the latter two cases, the expandablemember 100 can be used to trap the obstruction 244 against a wall of theblood vessel 234. The blood vessel 234 may be of the intracranialcerebrovasculature, such as an internal carotid artery, a middlecerebral artery, an anterior cerebral artery, a vertebral basilarartery, or a posterior cerebral artery, or may be in any other bodylumen or vessel.

As previously mentioned, the terms “proximal” and “distal” are usedherein for clarity of description and do not limit the positioning orarrangement of the structures of the present invention. In theorientation of FIGS. 6A-6C, blood within the vessel flows in abloodstream 246 direction, from the proximal catheter end 238 toward thedistal catheter end 240, and the obstruction 244 is accessed fromupstream. Since the bloodstream 246 may assist the operation of theexpandable member 100, one of ordinary skill in the art can readilydesign a suitable expandable member and corresponding deploymentapparatus which may be used in the opposite instance, when theobstruction 244 is accessed from downstream (not shown).

In FIG. 6A, the expandable member 100, in dashed line, is in the first,collapsed condition within the catheter lumen 242. The expandable member100 is attached to the guidewire 124, which is adapted for selectiveinsertion through the catheter lumen 242. As the guidewire 124 travelsthrough the catheter lumen 242, the expandable member 100 is carried tothe obstruction 244. At least one of the delivery catheter 232,guidewire 124, and expandable member 100 may include at least oneradiopaque portion/marker (not shown) to aid the user in visualizing theposition of the marked structure throughout the deployment procedure.

In FIG. 6B, the expandable member 100 is still in the collapsedcondition, but has exited the distal catheter end 240 and is locatedadjacent the obstruction 244. The site of deployment of all or a portionof the expandable member 100 is typically radially within theobstruction 244. However, the site of deployment can also be upstream ordownstream of the obstruction 244, with the expandable member 100 beingmoved, in a collapsed or partially expanded condition, to a positionradially within the obstruction. The obstruction 244 need not entirelyradially surround the expandable member 100; instead, the expandablemember could be deployed radially off-center with respect to theobstruction, or the obstruction 244 may not entirely cover the innercircumference of the blood vessel 234.

Generally in an intracranial application, the diameter of the expandablemember 100 may be between about 0.05-5 mm, e.g., about 0.016 mm, in thecollapsed state and between about 0.1-10 mm, e.g., about 5 mm, in theexpanded state. Similarly, and again for an intracranial application,the length of the expandable member 100 may be between about 5-60 mm,e.g., about 22 mm, in both the collapsed and expanded states, unless thedesign structure of the expandable member causes appreciable lengthchange during radial expansion and collapse. The dimensions of theexpandable member 100, like all structures described herein, are highlydependent upon the dimensions of the delivery catheter and body lumen inwhich the expandable member 100 travels and is deployed, respectively,and one of ordinary skill in the art can readily choose appropriatedimensions for all structures used in a particular application of thepresent invention.

Turning to FIG. 6C, the expandable member 100 is shown in the second,expanded condition within at least a portion of the obstruction 244. Thearrow depicting the expansion direction 248 indicates that a radiallyoutward force is exerted by the expandable member 100 against theadjacent obstruction 244. Though the expansion direction 248 is shown asbeing two-dimensional, the expandable member 100 will expand radially inall directions outward from the longitudinal axis 102 unless theexpandable member has been designed/configured for nonuniform expansion.

In the sequence of FIG. 6A-6C, the expandable member 100 exits thedelivery catheter 232 in the collapsed condition and is placed in thedesired position adjacent the obstruction 244 before being expanded intothe expanded condition. The expandable member 100 shown in FIGS. 6A-6Cmay self-expand once in position, for example, through use of atemperature-respondent shape-memory alloy. Alternately or additionally,the expandable member 100 may be manually expanded through use of aninflation balloon (not shown), in a known manner. That is, an inflationcatheter (not shown) carrying the inflation balloon may be provided forselective insertion through the catheter lumen 242. The expandablemember 100 is optionally crimped around the inflation balloon when inthe collapsed condition. In such a case, the inflation catheter mayreplace the guidewire 124 in performing the function of guiding and/orcarrying the expandable member 100 to the site of the obstruction 244.The inflation catheter, through the inflation balloon, then may beoperative to selectively manually expand the expandable member 100adjacent at least a portion of the obstruction 244. When an inflationballoon is used to expand the expandable member 100, the inflationballoon may be configured so as not to block the first interstices 112while the inflation balloon still exerts radially outward pressure onthe expandable member, to help provide compression and fragmentation ofthe obstruction 244 as described below.

In the sequence of FIGS. 7A-7D, a second mode of operation of theexpandable member 100 is depicted. As with the first mode of operation,a delivery catheter 232 is advanced downstream through a blood vessel234 to a position adjacent an obstruction 244. However, in the secondmode of operation, the expandable member 100 is at least partiallyconstructed of a superelastic and/or self-expanding material, such asnitinol which has been memory-shaped into an expanded condition and iscompressed into a collapsed condition before use. Therefore, theexpandable member 100 is constrained in the collapsed condition by thedelivery catheter 232 and self-expands into the expanded condition uponremoval from the delivery catheter.

FIG. 7A depicts the delivery catheter 232 with the guidewire 124extending from the distal catheter end 240 and through the obstruction244. In FIG. 7B, the delivery catheter 232 has been advanced over theguidewire 124 until the distal catheter end 240 is located radiallyadjacent at least a portion of the obstruction 244. The expandablemember 100, shown in dashed line in FIG. 7B within the delivery catheter232, is also located radially adjacent at least a portion of theobstruction 244. Though the guidewire 124 is shown and described asguiding both the expandable member 100 and the delivery catheter 232, asecondary guidewire (not shown) may be provided to assist in positioningthe delivery catheter; the secondary guidewire could then be exchangedfor the guidewire 124 for deployment of the expandable member.

During the transition from the view of FIG. 7B to that of FIG. 7C, theexpandable member 100 is maintained in position within the obstruction244 while the delivery catheter 232 is withdrawn in a proximal directionfrom the expandable member, thus exposing the distal member end 106.Because the expandable member 100 in the second mode of operation isself-expanding, the distal member end 106 begins to expand in a knownmanner in the expansion direction 248 as the expandable member isreleased by the delivery catheter 232.

FIG. 7D depicts the self-expanding expandable member 100 of the secondmode of operation in a fully expanded condition adjacent the obstruction244. Since the bloodflow direction 246 in the orientation of FIGS. 7A-7Dmoves proximal-to-distal, it is desirable for the distal member end 106to be closed and to be located downstream of the proximal member end104, which is also shown in FIGS. 7A-7D as being closed. As can be seenin FIG. 7D, the proximal and distal member ends 104 and 106 may beconnected to the guidewire 124 by the attachment collars 132.

As can be seen in the sequences of FIGS. 6A-6C and 7A-7D, theobstruction 244 becomes at least partially compressed against the bloodvessel 234 as the expandable member 100 expands, regardless of the meansby which such expansion occurs. This compression aids in increasingblood flow past the obstruction 244. The sequence of FIGS. 8A-8E depictsboth this compression and a separate erosion-type process as a combinedmechanism of operation through which any embodiment of the presentinvention increases blood flow through the obstructed blood vessel 234.

In FIG. 8A, the expandable member 100 is positioned adjacent theobstruction 244 with the proximal member end 104 located upstream of thedistal member end 106 (both shown here as being closed). The bloodflowdirection 246 is from left to right, in the orientation of FIGS. 8A-8E,and the expandable member 100 is exerting outward radial force in theexpansion direction 248. The force exerted by the expandable member 100depends on a number of factors, which include the properties of thematerial chosen for the expandable member. By suitably varying thesefactors, the force exerted by the expandable member 100 can becontrolled. The expandable member 100 may exert sufficient force tocause the member body 108, or another portion of the expandable member,to compress at least a portion of the obstruction 244 against a vesselwall 350 of the blood vessel 234.

In FIG. 8B, the force exerted by the expandable member 100 dislodges atleast one fragment 352 from the obstruction 244 and helps pass eachfragment 352 through a first interstice 112 in the radial direction intothe body interior 122. In other words, at least one of the plurality offirst strands 114 may penetrate into the obstruction 244 tolongitudinally separate each fragment 352 from a remaining portion ofthe obstruction.

The action by which the expandable member 100 dislodges the fragments352 may vary depending upon the composition of the obstruction 244. Forexample, when the obstruction 244 is made up of a relatively softmaterial, the first strands 114 may slice radially into the obstruction244 and the fragments 352 will protrude into the expandable member 100in an extruding manner. If the obstruction 244 is made up of a hardermaterial, pressure from the first strands 114 may instead flake offfragments 352 in a fracturing manner. Optionally, the expandable member100 may be adapted for at least a small degree of rotation about thelongitudinal axis 102. Such rotation, once the first strands 114 are atleast partially embedded in the obstruction 244, may help to free thefragments 352 from the obstruction 244 by severance in a circumferentialdirection about the longitudinal axis 102.

Whether or not the expandable member 100 is rotated, blood flowing inthe bloodflow direction 246 will exert pressure on the fragments 352 tohelp separate the fragments from the obstruction 244. The fragments 352,once free within the member body 108, are then carried by the blood inthe bloodflow direction 246 toward the (closed) distal member end 106,where the fragments collect as shown in FIG. 8C.

If one or more of the fragments 352 is smaller than one of the secondinterstices 118, the fragment will pass through that second intersticeand out of the expandable member 100 in a downstream direction. To thisend, the size of at least one of the plurality of first interstices 112and/or the plurality of second interstices 118 may be chosen dependingupon an allowable particulate size of the blood vessel 234. Thisallowable particulate size may vary, depending upon the size andlocation of the blood vessel 234, the size and location of othervasculature in fluid connection downstream from the blood vessel 234,the presence of any pharmaceutical agents and/or other medical deviceswithin the blood vessel 234, or any other factors. The size of fragment352 which may pass through the first and second interstices 112 and 118will vary depending upon at least the position of that interstice on themember body 108, the degree of expansion of the expandable member 100,the shape of the fragment 352, and the orientation of the intersticewith respect to the bloodflow direction 246. For example, if a certaininterstice (particularly a second interstice 118) is orientedsubstantially perpendicularly to the longitudinal axis 108, a largerfragment 352 may more readily pass through that interstice than if theinterstice were at an oblique angle with respect to the longitudinalaxis. One of ordinary skill in the art can readily design first andsecond meshes 110 and 116 having desired properties to selectivelyretain the fragments 352 in a suitable manner for a particularapplication of the present invention.

If a fragment 352 is too large to pass through a second interstice 118and flow downstream of the expandable member 100, at least one of theplurality of second strands 120 may break the fragment into a pluralityof subfragments 354. At least one of the second interstices 118 may thenallow passage therethrough of at least one subfragment 354 to releasethe subfragment 354 from the expandable member 100. The second strand120 breaks the fragment 352 into subfragments 354 in a similar manner tothat in which the first strand 114 dislodges the fragment from theobstruction 244. Namely, pressure exerted on the fragment 352 in thebloodflow direction 246 by flowing blood and/or other fragmentscollected at the distal member end 106 forces the fragment into contactwith the second strand 120. When the pressure becomes sufficient toovercome the mechanical resistance of the fragment 352, the fragmentbegins to be extruded or fractured through the second interstice 118, asshown in FIG. 8D. The subfragments 354 thereby formed exit theexpandable member 100 and are carried away from the site of theobstruction 244 by bloodflow through the blood vessel 234.

In addition to this mechanical lysing provided by the second strands120, the fragments 352 could also undergo chemical lysing to enhance thebreakup of the obstruction 244. A pharmaceutical agent (not shown) couldbe provided to at least partially lyse at least one fragment 352 and/orsubfragment 354. The pharmaceutical agent may be eluted by theexpandable member 100, as previously mentioned. Additionally oralternatively, the pharmaceutical agent may be provided via the deliverycatheter 232 at a location adjacent the obstruction 244. Moreover, thepharmaceutical agent could be locally or systemically provided to thepatient in another manner. Regardless of the manner of provision of thepharmaceutical agent, chemical lysing will be operative upon at leastone of the obstruction 244, a fragment 352, and/or a subfragment 354.Chemical lysing agents are most effective upon structures having a largeratio of surface area to volume, so it is advantageous to mechanicallybreak up the obstruction 244 into smaller pieces (such as fragments 352and/or subfragments 354) to decrease the time required for theobstruction 244 to chemically lyse.

As shown in FIG. 8D, the expandable member 100 continues to exertpressure upon the obstruction 244 in the expansion direction 248 asfragments 352 are dislodged from the obstruction. Therefore, as thevolume of the obstruction 244 is reduced by loss of the fragments 352and/or by compression of the obstruction 244 toward the vessel wall 350,more blood will be able to flow through the volume-diminishedobstruction 244. The increased bloodflow past the obstruction 244 willhelp to mechanically lyse the obstruction, whether or not the expandablemember 100 continues to dislodge fragments 352 from the obstruction.Stasis (e.g., that caused by an obstruction 244) in a blood vessel 234allows for factors which promote obstructions to accumulate, therebymaintaining the obstruction in the blood vessel. Reestablishing orenhancing blood flow washes away and dilutes these factors and promoteserosion of the obstruction 244. Additionally, the increased bloodflowwill exert increased pressure on the collected fragments 352 at thedistal member end 106, potentially enhancing the mechanical lysing ofthe fragments into subfragments 354.

Optionally, an aspiration catheter (not shown) is adapted for selectiveinsertion through the catheter lumen 242. The aspiration catheter, whenpresent, is operative to selectively remove at least one fragment 352from the expandable member 100 under suction power. The aspirationcatheter may place the body interior 122 into direct fluid communicationwith a suction source (not shown) to directly remove the fragment 352from within the expandable member 100. Alternately, the aspirationcatheter may exert suction power upon the fragment 352 from an outsideposition adjacent the proximal or distal member ends 104 or 106 tosupplement the pressure naturally provided in the bloodflow direction246 and thereby pull the fragment through a second interstice 118,either into the aspiration catheter for removal from the body or toenhance release of the fragment into the blood vessel 234 downstream ofthe expansion member 100. The use of such an aspiration catheter may bedesirable if fragments 352 collecting at the distal member end 106 arenot exiting the expandable member 100 and are reducing bloodflow throughthe expandable member in an unwanted manner.

Once the obstruction 244 has been fragmented and depleted as desired,the expandable member 100 may be collapsed from the expanded conditionto the collapsed condition and removed from the blood vessel 234 throughthe delivery catheter 232. FIG. 8E depicts the expandable member 100 inthe process of collapsing. The expandable member 100 is maintained inposition inside the blood vessel 234, and the delivery catheter is movedin a sheathing direction 356 (opposite the bloodflow direction 246) toenvelop the expandable member. The expandable member 100 will beconstrained into the collapsed condition upon contact with the distalcatheter end 240 and can then be held within the catheter lumen 242 forremoval from the blood vessel 234.

In another, alternate mode of removal (not shown), the delivery catheter232 could be maintained in position so that the guidewire 124 can bepulled in the bloodflow direction 246. The guidewire in this alternateremoval mode thus pulls an attached expandable member 100 into arelatively stationary delivery catheter. However, care should be takenduring movement of the expandable member 100 to avoid mechanical traumato the vessel wall 350. In any mode of removal, the delivery catheter232 and the expandable member 100 can both or either move to produce arelative sheathing motion between these two structures.

It is contemplated that the expandable member 100 can be collapsed fromthe expanded condition into the collapsed condition in any suitablemanner, and then moved rotationally and/or longitudinally within theblood vessel 234 while constrained, such as through a motion of thedelivery catheter 232 enclosing the expandable member. The expandablemember 100, once positioned as desired, may then be re-expanded from thecollapsed condition to the expanded condition. Such redeployment may beuseful, for example, when the obstruction 244 has a longitudinaldimension greater than that of the expandable member 100 or when thesame expandable member is operative on a plurality of spaced-apartobstructions 244. The expandable member 100 may be collapsed andredeployed any number of times, as desired by the user.

Regardless of whether the expandable member 100 is redeployed within theblood vessel 234, it may be desirable to finally remove the expandablemember from the blood vessel once a suitable blood flow rate isreinstated in the blood vessel across the site of the treatedobstruction 244. For example, angiography can be performed to assessblood flow, with additional mechanical and/or chemical lysing beingperformed until the blood flow has achieved a suitable rate for apredetermined period of time—for example, between about 10-15 minutes.

When the expandable member 100 is removed from the patient's body, acuteand chronic anti-platelet therapy is no longer necessary to prevent theexpandable member from causing future obstructions. Such acute andchronic anti-platelet therapy may increase the likelihood of developmentof complication, such as an intracranial hemorrhage, associated withother methods of acute revascularization. An intracranial hemorrhageoccurring when the patient's system contains pharmaceutical agents forchemical lysing may be fatal. Even when no chemical lysing oranti-platelet agents are present, surgical treatment for an intracranialhemorrhage is fraught with postoperative complications. Therefore, itmay be desirable for the expandable member 100 to be removed from thepatient's body.

Optionally, the expandable member 100 may be removed from the bloodvessel 234 before the structures of the expandable member heal into thevessel wall 350. For example, the expandable member 100 may be removedin the above manner from about one (1) minute to about 48 hours afterdelivery of the device, with re-operation possibly being required forremoval toward the latter portion of that range of time. However, whenthe expandable member 100 is intended to remain in the patient's bodyfor an extended period of time, the expandable member should be adaptedfor release from the guidewire 124, preferably when the expandablemember is in the expanded condition at the desired implantation locationwithin the blood vessel 234. The release may be carried out in anysuitable manner, using any desired mechanical, chemical, electrolytic,temperature-sensitive, remotely-triggered, or other type of releasemeans.

At least one fragment 352 may be carried from the blood vessel 234within the expandable member 100 as the expandable member is withdrawnthrough the delivery catheter 232. Additionally, the force exerted bythe distal catheter end 240 on the expandable member 100 may squeeze thefragments 352 collected at the distal member end 106 against the firstor second strands 114 or 120. Such squeezing force may cause extrusionor flaking of the fragments into subfragments 354, which are thenreleased into the blood vessel 234 as shown in FIG. 8E. The first andsecond meshes 110 and 116 should be designed such that these delayedsubfragments 354 do not exceed the allowable particulate size of theblood vessel 234.

While aspects of the present invention have been particularly shown anddescribed with reference to the preferred embodiment above, it will beunderstood by those of ordinary skill in the art that various additionalembodiments may be contemplated without departing from the spirit andscope of the present invention. For example, the member body 108 couldhave a round, ovoid, rectilinear, curvilinear, or any other desiredcross-sectional shape. The expandable member 100 can expand or collapsein a radial, circumferential, and/or longitudinal direction. Like alldescribed structures, the expandable member 100 may be made of anymaterials and in any dimensions, as appropriate for a particularapplication of the present invention. The expanded and collapsedconditions of the expandable member 100 are not strict binary limitsupon the condition of the expandable member, but represent more generalranges of condition (e.g., an expandable member in the “expanded”condition may be able to expand further as the obstruction 244 is erodedand/or compressed). Several of the first strands 114 may performfunctions of the second strands 120 and vice versa, particularly if thedivisions between the member body 108 and proximal/distal member ends104 and 106 are not sharply delineated. Likewise, certain strands mayfunction as both first and second strands 114 and 120 at various pointsalong the length thereof. The expandable member 100 can be used inconjunction with lytic agents (tPA and IIb/IIIa inhibitors), and canalso be used with various microcatheters, guidewires and endovascularaccess devices that are currently commercially available. Operation ofthe expandable member 100 is described as being assisted by bloodflowwithin the blood vessel 234, but the present invention is also operablewhen bloodflow is intentionally or inadvertently reduced or eliminatedwithin the blood vessel 234. The expandable member 100 is described asperforming a filtering function upon fragments 352 dislodged from theobstruction 244, but could also or instead provide a filtering functionto existing fragments (not shown) in the bloodstream which did notoriginate with the obstruction. A device or method incorporating any ofthese features should be understood to fall under the scope of thepresent invention as determined based upon the claims below and anyequivalents thereof.

Other aspects, objects, and advantages of the present invention can beobtained from a study of the drawings, the disclosure, and the appendedclaims.

We claim:
 1. A method of removing an obstruction from a blood vessel with an expandable member that is attached to a delivery system, the expandable member having a proximal end, a distal end and a tubular body between the proximal end and the distal end, the tubular body being made of a mesh having a plurality of interstices, the method comprising the steps of: positioning the tubular body of the expandable member radially adjacent to an obstruction within a blood vessel; expanding the expandable member such that a portion of the tubular body comes into contact with a portion of the obstruction; dislodging a portion of the obstruction to enhance blood flow through the blood vessel past the obstruction; and removing the expandable member from the blood vessel while the expandable member retains at least a portion of the obstruction from the blood vessel; wherein the step of removing the expandable member is performed with the expandable member in a fully expanded position.
 2. The method of claim 1, wherein the expandable member is permanently attached to the delivery system.
 3. The method of claim 1, wherein the expandable member is releasably attached to the delivery system.
 4. The method of claim 1, wherein the dislodging step includes fracturing a portion of the obstruction.
 5. The method of claim 4, wherein the removing step includes removing the fractured portion of the obstruction.
 6. The method of claim 1, wherein the dislodging step includes extruding a portion of the obstruction.
 7. The method of claim 6, wherein the removing step includes removing the extruded portion of the obstruction.
 8. The method of claim 1, further comprising the step of increasing the blood flow rate in the blood vessel.
 9. The method of claim 1, further comprising the step of chemically lysing the obstruction.
 10. The method of claim 9, wherein the step of chemically lysing includes providing a pharmaceutical agent.
 11. The method of claim 10, wherein the step of chemically lysing includes eluting the pharmaceutical agent from the expandable member.
 12. The method of claim 10, wherein the step of chemically lysing includes providing the pharmaceutical agent via the delivery system.
 13. The method of claim 1, wherein the expandable member is expanded radially.
 14. The method of claim 1, wherein the expandable member is self-expanding.
 15. The method of claim 1, wherein the expandable member is manually expanded.
 16. The method of claim 1, further comprising the step of connecting at least a portion of the obstruction to the expandable member.
 17. The method of claim 1, wherein the blood vessel is a cerebral blood vessel.
 18. The method of claim 1, wherein the blood vessel is a blood vessel other than a cerebral blood vessel.
 19. The method of claim 1, wherein the dislodging step occurs before the removing step.
 20. The method of claim 1, wherein the dislodging step comprises separating a portion of the obstruction from the remainder of the obstruction.
 21. The method of claim 1, wherein the dislodging a portion of the obstruction step includes at least a portion of the obstruction passing through at least one of the plurality of interstices. 